Two time series data (1. Engine RPM wrt time and 2. Seat Acceleration wrt time) were analyzed using LMS Testlab and LMS AMESim post processing tools. It was observed that the order plot of acceleration wrt rpm obtained from both softwares using the same window type and trend removal option do not match. Further investigations reveals that using the same sampling frequency in AMESim and Testlab produced a result that have similar trends with Testlab result. However, the accelerations amplitudes have significant deviation from Testlab results.
What other parameters should be checked to obtain same results from Testlab and AMESim?
Best Regards,
David
Hi David
Debugging software always is dog's work.
Suggestions on simple things to compare are
- RMS (1s) values computed from raw time signals to ensure signals have similar energy content.
- Autospectrum, verify that frequencies and amplitudes are identitical. Check Autospectrum with Amplitude shown as Peak, RMS, Pk-Pk etc.
- A good overview of long time series often is to use Amplitude histograms and to look at Kurtosis.
Where possible, try and swap data between systems, i.e. get test data to act as simulation data and vice versa. If this works, use a simple calibrator signal of 1 g at fixed and known frequency as first signal to test AMESim.
If I should venture a guess, test systems use fixed sampling rates as the measurement HW uses fixed clock frequency. A simulation system may use different time steps because of numerical efficiency and this difference in time stepping may complicate post processing.
Have fun
Claes
Hi Claes,
Thank you so much for your suggestions. I want to clarify my problem statement which is simply stated as:
For a given time series data, compare the order plots (extracted from the waterfall plot) by postprocessing the data in Testlab and AMESim.
The results are shown in the attached file. Kindly let me know your observations.
Best regards,
David
Hi David
Start simple. Take out X seconds of data at one RPM and make sure RMS is in the same ballpark. Next, do an FFT of the time signal and compare spectrum.
If comparison does not pass this stage, then it will not pass other stages when dependent on RPM or Order.
/Claes
Thank you very much Claes for your insightful suggestion.
Regards,
David
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